Spectrokinetic Studies of the Gas Phase Reactions NH2 + NOx Initiated by Pulse Radiolysis.

Pagsberg, P.; Sztuba, Barbara; Ratajczak, Emil; Sillesen, Alfred; Pellicer, J.

doi:10.3891/acta.chem.scand.45-0329

Cited by 30 publications

(34 citation statements)

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“…17 The LIF results from Hack et al 14 lie a factor of 2−4 below other studies, and apparently, some unrecognized interference was present. By contrast to the present LIF work, experiments based on optical absorption should not be sensitive to the intensity of the probe beam, and the results of Bulatov et al 18 and Pagsberg et al 19 agree with the present work at room temperature. The temperature dependence obtained by Bulatov et al is somewhat more negative than measured here, leading to a difference of about a factor of 1.5 at 600 K.…”

Section: ■ Experimental Resultssupporting

confidence: 69%

“…The high and low-pressure limit rate constants are reproduced accurately over the 300−2000 K temperature range by the following modified Arrhenius expressions (cm 3 molecule −1 s −1 ): where T is in K. These predictions are compared with the prior experimental and theory/modeling results for the total rate coefficient [13][14][15][16][17][18][19]22 in Figure 4 and for the branching ratio 13,20−25 in Figure 9. The present theoretical predictions for the overall rate constant are seen to be in good agreement with our experimental results, but are about a factor of 3 lower than the high-temperature results of Song et al 22 The branching to the HNNO + OH channels, of minor significance at high temperatures, is clearly not sufficient to explain this discrepancy.…”

Section: ■ Experimental Resultsmentioning

confidence: 83%

“…"This Work" denotes the present theoretical rate constant, while "Present" denotes the experimental results obtained in the present study. Literature data: Glarborg, 13 Song, 22 Xiang, 17 Pagsberg, 19 Whyte, 16 Hack, 14 Bulatov,18 and Kurosawa. 15 harmonic results, both obtained at the B3LYP/6-311++G(d,p) level.…”

Section: ■ Experimental Resultsmentioning

confidence: 99%

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Rate Constant and Branching Fraction for the NH₂ + NO₂ Reaction

et al. 2013

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The NH 2 + NO 2 reaction has been studied experimentally and theoretically. On the basis of laser photolysis/LIF experiments, the total rate constant was determined over the temperature range 295−625 K as k 1,exp (T) = 9.5 × 10 −7 (T/K) −2.05 exp(−404 K/T) cm 3 molecule −1 s −1 . This value is in the upper range of data reported for this temperature range. The reactions on the NH 2 + NO 2 potential energy surface were studied using high level ab initio transition state theory (TST) based master equation methods, yielding a rate constant of k 1,theory (T) = 7.5 × 10 −12 (T/K) −0.172 exp(687 K/T) cm 3 molecule −1 s −1 , in good agreement with the experimental value in the overlapping temperature range. The two entrance channel adducts H 2 NNO 2 and H 2 NONO lead to formation of N 2 O + H 2 O (R1a) and H 2 NO + NO (R1b), respectively. The pathways through H 2 NNO 2 and H 2 NONO are essentially unconnected, even though roaming may facilitate a small flux between the adducts. High-and low-pressure limit rate coefficients for the various product channels of NH 2 + NO 2 are determined from the ab initio TST-based master equation calculations for the temperature range 300−2000 K. The theoretical predictions are in good agreement with the measured overall rate constant but tend to overestimate the branching ratio defined as β = k 1a /(k 1a + k 1b ) at lower temperatures. Modest adjustments of the attractive potentials for the reaction yield values of k 1a = 4.3 × 10 −6 (T/K) −2.191 exp(−229 K/T) cm 3 molecule −1 s −1 and k 1b = 1.5 × 10 −12 (T/K) 0.032 exp(761 K/T) cm 3 molecule −1 s −1 , in good agreement with experiment, and we recommend these rate coefficients for use in modeling. ■ INTRODUCTIONThe formation and consumption of nitrogen oxides (NO x ) at high temperatures continue to be an important area of research. Of particular interest is the chemistry of amine radicals. Ammonia is formed in significant quantities in devolatilization of solid fuels 1 and the selectivity in oxidation of amine radicals to form NO or N 2 is important for the yield of NO x . 2 Reactions of amine radicals are also important for the performance of selective noncatalytic reduction (SNCR) of NO using aminebased additives such as ammonia or urea. In the past, both NH 3 oxidation 2−6 and SNCR 2,7−11 have been studied extensively within combustion.Following the detection of NO 2 as an important intermediate in SNCR, 12 the reaction of NH 2 with NO 2 was identified as a key step. 9,11 This reaction has two major product channels:(R1a)The prior analysis of Glarborg et al. 13 provides an overall picture of the kinetics for this reaction. The NH 2 radical can add to either the N atom of NO 2 to form H 2 NNO 2 or one of the O atoms to form H 2 NONO. The H 2 NNO 2 species ultimately produces N 2 O + H 2 O (R1a) after a number of isomerizations. Meanwhile, the H 2 NONO species directly dissociates to H 2 NO + NO (R1b). Both of these sets of products are exothermic relative to reactants, and the transition states on the pathway to forming N...

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Section: ■ Experimental Resultssupporting

confidence: 69%

Section: ■ Experimental Resultsmentioning

confidence: 83%

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Rate Constant and Branching Fraction for the NH₂ + NO₂ Reaction

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“…There is now substantial agreement on the overall rate coefficient (Atakan et al 1989;Bulatov et al 1989;Pagsberg et al 1991;Baulch et al 1992;Diau et al 1994;Wolf et al 1994) and growing evidence that the branching ratio {3, that is, kI8b/(kI8a + kI8b), is smaller than previously believed, particularly at lower temperatures. For example, six investigations subsequent to the Hanson and Salimian review (Dolson 1986;Hall et al 1986;Silver and Kolb 1987;Atakan et al 1989;Bulatov et al 1989;Pagsberg et al 1991) uniformly reported {3 values in the range from 0.1 to 0.15 at room temperature; Baulch et al (1992) recommend {3 = 0.12 at 298 K. The temperature dependence of {3 is controversial. Atakan et al and Bulatov et al report that it increases slightly with temperature, while Park and Lin (1996) and Halbgewachs et al (1996) report stronger dependences.…”

Section: Nh2 + Nh2 --Productsmentioning

confidence: 85%

Combustion Chemistry of Nitrogen

Dean

Bozzelli

2000

Gas-Phase Combustion Chemistry

233

317

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“…More recently, both the rate and products of the reaction of NH 2 with NO have been the focus of a number of direct determinations between room temperature and ca. 1000 K. − At higher temperatures modeling has been used to determine products of the reaction. − Portions of the potential energy surface have also been calculated over the past 15 years, − although all of the thermally accessible stationary points had not been treated before the present work.…”

Section: Introductionmentioning

confidence: 99%

A Comprehensive Study of the Reaction NH₂+ NO → Products: Reaction Rate Coefficients, Product Branching Fractions, andab InitioCalculations

1997

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We have undertaken a comprehensive study of the reaction NH2(X2B1) + NO → N2 + H2O (1a) and NH2(X 2B1) + NO → N2H + OH → N2 + H + OH (1b). Experimental measurements of the reaction rate coefficient and product branching fraction are combined with accurate ab initio calculations to give a detailed picture of this important reaction. The rate constant of reaction 1 was investigated in the temperature range 203 K ≤ T ≤ 813 K using the laser photolysis/CW laser-induced fluorescence technique for production and detection of NH2. The rate coefficient was found to be pressure independent between 10 and 100 Torr and is well described by k 1(T) = 1.65 × 10-7 T -1.54 exp (−93 K/T) cm3/(molecule·s). The deuterium kinetic isotope effect for the reactions of NH2 and ND2 with NO was investigated at temperatures between 210 and 481 K. A small, temperature-independent isotope effect of k H/k D = 1.05 ± 0.03 was found. Additional experimental work focused on measuring the product branching fraction for production of OH, Φ1b, and its deuterium isotope effect at room temperature. Measurements were performed using the discharge-flow technique with mass spectrometric detection of products. OH from channel 1b was reacted with excess CO and measured as CO2. The room temperature branching fraction was measured as Φ1b = 9.0 ± 2.5% (NH2 + NO; T = 298 K) and Φ1b = 5.5 ± 0.7% (ND2 + NO; T = 298 K). Theoretical calculations have characterized the stationary points on the potential energy surface connecting reactants with products using G2 and G2Q levels of theory. These calculations support the experimentally observed temperature dependences and kinetic isotope effects.

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Spectrokinetic Studies of the Gas Phase Reactions NH2 + NOx Initiated by Pulse Radiolysis.

Cited by 30 publications

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Rate Constant and Branching Fraction for the NH₂ + NO₂ Reaction

Rate Constant and Branching Fraction for the NH₂ + NO₂ Reaction

Combustion Chemistry of Nitrogen

A Comprehensive Study of the Reaction NH₂+ NO → Products: Reaction Rate Coefficients, Product Branching Fractions, andab InitioCalculations

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Spectrokinetic Studies of the Gas Phase Reactions NH2 + NOx Initiated by Pulse Radiolysis.

Cited by 30 publications

References 0 publications

Rate Constant and Branching Fraction for the NH2 + NO2 Reaction

Rate Constant and Branching Fraction for the NH2 + NO2 Reaction

Combustion Chemistry of Nitrogen

A Comprehensive Study of the Reaction NH2+ NO → Products: Reaction Rate Coefficients, Product Branching Fractions, andab InitioCalculations

Contact Info

Product

Resources

About

Rate Constant and Branching Fraction for the NH₂ + NO₂ Reaction

Rate Constant and Branching Fraction for the NH₂ + NO₂ Reaction

A Comprehensive Study of the Reaction NH₂+ NO → Products: Reaction Rate Coefficients, Product Branching Fractions, andab InitioCalculations